Powertrain for electric vehicle

ABSTRACT

A powertrain for an electric vehicle includes: a planetary gear including a first rotating element, a second rotating element, and a third rotating element, where the first rotating element is connected to a first shaft, the second rotating element is connected to a second shaft, and the third rotating element is selectively connected to a transmission housing; a first motor supplying power to the first shaft at all times; and a second motor selectively supplying power to the first shaft and the second shaft. Two rotating elements among the first, second, third rotating elements of the planetary gear are selectively connected to integrally rotate the entire planetary gear.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of non-provisional U.S.patent application Ser. No. 16/887,267, filed on May 29, 2020, whichclaims priority to and the benefit of Korean Patent Application Nos.10-2019-0141771, filed on Nov. 7, 2019 and 10-2020-0025247, filed onFeb. 28, 2020, the entire contents of each of which are incorporatedherein by reference.

FIELD

The present disclosure relates to technology of powertrains provided inelectric vehicles.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Electric vehicles (EVs) are vehicles using power provided by electricmotors for propulsion. Such electric vehicles can significantlycontribute to the reduction of environmental pollution in metropolitanareas in that there are no emissions.

For the popularization of such electric vehicles, the improvement ofvarious technologies is desired. In particular, a technology forsignificantly increasing a drivable range after charged once is desired.

To increase the drivable range, vehicles should be able to satisfymaximum gradeability and maximum speed desired for a vehicle whileimproving fuel efficiency (i.e., a driving range per unit of electricalenergy (km/kWh)) by reducing the size and capacity of a motor disposedin an electric vehicle. In this regard, a transmission is disposed in anelectric vehicle.

For the above-described reasons, the transmission disposed in theelectric vehicle has high power transfer efficiency due to a relativelysimple configuration while avoiding either torque interruption in whichtorque transferred to driving wheels is interrupted or a gear shiftingshock during gear shifting.

The information disclosed in the Background of the Disclosure section isonly for the enhancement of understanding of the background of thedisclosure, and should not be taken as an acknowledgment or as any formof suggestion that this information forms a prior art that would alreadybe known to a person skilled in the art.

SUMMARY

The present disclosure provides a powertrain for an electric vehicle,and the powertrain is able to satisfy maximum gradeability and maximumspeed desired for a vehicle while reducing the capacity of a motor byproviding a plurality of shift ratios, to improve electrical efficiencyof the vehicle by realizing high power transfer efficiency using arelatively simple configuration and a relatively small weight, and toprevent torque interruption and shift shock.

In accordance with an aspect of the present disclosure, a powertrain foran electric vehicle may include: a planetary gear having three rotatingelements (i.e., first, second and third rotating elements), where thefirst rotating element is connected to a first shaft and the secondrotating element is connected to a second shaft; a first motor installedto selectively supply power to the first shaft at two or more gearratios; and a second motor installed to selectively supply power to thefirst shaft and the second shaft.

The third rotating element of the planetary gear may be selectivelyconnected to a transmission housing, and two rotating elements among thethree rotating elements of the planetary gear may be selected to beconnected to each other, such that the entire planetary gear is rotatedintegrally.

A first shift assembly may be provided between the first motor and thefirst shaft to switch between a state in which power provided by thefirst motor is transmitted directly to the first shaft and a state inwhich power provided by the first motor is shifted by a gear trainbefore being transmitted to the first shaft.

In one form, a rotating shaft of the first motor is coaxial with thefirst shaft. The first shift assembly may include a gear engagementunit, a hub and a sleeve, which are provided on a rotating shaft of thefirst motor. A first gear including a clutch gear configured to engagewith the sleeve of the gear engagement unit may be rotatably disposed onthe rotating shaft of the first motor. A second gear including a clutchgear configured to engage with the sleeve of the gear engagement unitmay be disposed on the first shaft such that rotation of the second gearis restrained.

A third gear in external engagement with the first gear and a fourthgear in external engagement with the second gear may be coaxiallyconnected to each other.

A first shift assembly may be provided between the first motor and thefirst shaft such that the power provided by the first motor istransmitted to the first shaft through one gear train of two externalengagement gear trains having different gear ratios.

In some forms of the present disclosure, the first shift assembly mayinclude a gear engagement unit, a hub and a sleeve of which are providedon a rotating shaft of the first motor. A first gear and a second gearmay be rotatably provided on both sides of the hub. A third gear inexternal engagement with the first gear and a fourth gear in externalengagement with the second gear may be coaxially connected to eachother. A fifth gear may be disposed on the shaft of the third gear andthe fourth gear such that rotation of the fifth gear is restrained. Asixth gear in external engagement with the fifth gear may be disposed onthe first shaft such that rotation of the sixth gear is restrained.

In some forms of the present disclosure, a seventh gear may be connectedto the first shaft such that rotation of the seventh gear is restrained.An eighth gear may be connected to the second shaft such that such thatrotation of the eighth gear is restrained. A ninth gear in externalengagement with the seventh gear and a tenth gear in external engagementwith the eighth gear may be disposed coaxially with each other. Thesecond motor may be disposed to be connectable to the first shaft andthe second shaft via a second shift assembly disposed between the ninthgear and the tenth gear.

In some forms of the present disclosure, the second shift assembly mayinclude a gear engagement unit, a hub and a sleeve of which are providedon a rotating shaft of the ninth gear and the tenth gear.

In another form, the second motor may be coaxially disposed on the firstshaft. The second motor may be configured such that the power providedby the second motor is transmitted to the first shaft or the secondshaft through an eleventh gear disposed concentrically on the firstshaft and a twelfth gear in external engagement with the eleventh gearto be coaxial with the ninth gear and the tenth gear.

The powertrain may further include a third shift assembly fixing thethird rotating element of the planetary gear to the transmission housingor connecting the third rotating element of the planetary gear to thesecond shaft by linear displacement following an axial direction of thefirst shaft.

In accordance with another aspect of the present disclosure, apowertrain for an electric vehicle. The powertrain may include: aplanetary gear having a first rotating element, a second rotatingelement and a third rotating element, where the first rotating elementis connected to a first shaft, the second rotating element is connectedto a second shaft, and the third rotating element is connected to athird shaft; a first motor configured to selectively supply power to thefirst shaft at two or more gear ratios; and a second motor configured toselectively supply power to the first shaft and the second shaft. Thethird shaft may be fixedly disposed on a transmission housing, and anytwo shafts among the first, second, and third shafts may restrain eachother.

Further, in accordance with yet another aspect of the presentdisclosure, there is provided a powertrain for an electric vehicle. Thepowertrain may include: a planetary gear including three rotatingelements (i.e., a first rotating element, a second rotating element anda third rotating element), among which the first rotating element isconnected to a first shaft, the second rotating element is connected toa second shaft, and the third rotating element is selectively connectedto a transmission housing; a first motor configured to supply power tothe first shaft at all times; and a second motor configured toselectively supply power to the first shaft and the second shaft. Anytwo rotating elements among the three rotating elements of the planetarygear are selectively connected to integrally rotate the entire planetarygear.

The first rotating element of the planetary gear may be a sun gear; thesecond rotating element of the planetary gear may be a carrier; and thethird rotating element of the planetary gear may be a ring gear.

In some forms of the present disclosure, a seventh gear may be connectedto the first shaft in a restrained state, an eighth gear may beconnected to the second shaft in a restrained state, a ninth gear inexternal engagement with the seventh gear and a tenth gear in externalengagement with the eighth gear may be installed coaxially with eachother, and the second motor may be installed to be connectable to thefirst shaft and the second shaft via a second shift assembly installedbetween the ninth gear and the tenth gear.

In some forms of the present disclosure, the second shift assembly mayinclude a gear engagement unit, a hub and a sleeve of which are providedon a rotating shaft of the ninth gear and the tenth gear.

In some forms of the present disclosure, the second motor may becoaxially installed on the first shaft; and power of the second motormay be transmitted to the first shaft or the second shaft by an eleventhgear installed coaxially on the first shaft and a twelfth gear inexternal engagement with the eleventh gear to be coaxial with the ninthgear and the tenth gear.

In some forms of the present disclosure, the powertrain may furtherinclude a third shift assembly configured to fix the third rotatingelement of the planetary gear to the transmission housing or connect thethird rotating element of the planetary gear to the second shaft bylinear displacement following an axial direction of the first shaft.

Further, in accordance with yet another aspect of the presentdisclosure, there is provided a powertrain for an electric vehicle. Thepowertrain may include: a planetary gear including three rotatingelements, among which a first rotating element is connected to a firstshaft, a second rotating element is connected to a second shaft, and athird rotating element is connected to a third shaft; a first motorconfigured to supply power to the first shaft at all times; and a secondmotor configured to selectively supply power to the first shaft and thesecond shaft. The third shaft is fixedly connected to a transmissionhousing, and any two shafts among the first, second, and third shaftsare configured to restrain each other.

Further, in accordance with yet another aspect of the presentdisclosure, there is provided a powertrain for an electric vehicle. Thepowertrain may include: a planetary gear including three rotatingelements, among which a first rotating element is connected to a firstshaft, a second rotating element is connected to a second shaft, and athird rotating element is selectively connected to a transmissionhousing; a second motor configured to supply power to the second shaftat all times; and a first motor configured to selectively supply powerto the first shaft and the second shaft. Any two rotating elements amongthe three rotating elements of the planetary gear are selectivelyconnected to integrally rotate the entire planetary gear.

In some forms of the present disclosure, the first rotating element ofthe planetary gear may be a sun gear; the second rotating element of theplanetary gear may be a carrier; and the third rotating element of theplanetary gear may be a ring gear.

In some forms of the present disclosure, a first shift assembly may beprovided between the second motor and the second shaft and configured toswitch between a state in which power of the second motor is directlytransmitted to the second shaft and a state in which the power of thesecond motor is transmitted to the first shaft by shifting of a geartrain.

In some forms of the present disclosure, a rotating shaft of the secondmotor is coaxial with the second shaft;

the first shift assembly may include a gear engagement unit, a hub and asleeve of which are provided on the rotating shaft of the second motor;a first gear including a clutch gear engageable with the sleeve of thegear engagement unit may be rotatably installed on the rotating shaft ofthe second motor; the clutch gear configured to engage with the sleeveof the gear engagement unit may be installed on the second shaft in astate in which rotation of the clutch gear is strained; and a secondgear may be installed on the first shaft and configured to receive thepower of the second motor in a state in which rotation of the secondgear is restrained.

In some forms of the present disclosure, a third gear in externalengagement with the first gear and a fourth gear in external engagementwith the second gear may be coaxially connected to each other.

In some forms of the present disclosure, the powertrain may furtherinclude a third shift assembly configured to fix the third rotatingelement of the planetary gear to the transmission housing or connect thethird rotating element of the planetary gear to the second shaft bylinear displacement following an axial direction of the first shaft.

In some forms of the present disclosure, a first shift assembly may beprovided between the second motor and the first shaft to switch betweena state in which power of the second motor is directly transmitted tothe first shaft and a state in which the power of the second motor istransmitted to the second shaft by shifting of a gear train.

In some forms of the present disclosure, the second motor may bedisposed such that a rotating shaft thereof is coaxial with the firstshaft; the first shift assembly may include a gear engagement unit, ahub and a sleeve of which are provided on the rotating shaft of thesecond motor; a first gear including a clutch gear configured to engagewith the sleeve of the gear engagement unit may be rotatably installedon the rotating shaft of the second motor; the clutch gear configured toengage with the sleeve of the gear engagement unit may be installed onthe first shaft in a state in which rotation of the clutch gear isstrained; and a second gear may be installed on the second shaft andconfigured to receive the power of the second motor in a state in whichrotation of the second gear is restrained.

In some forms of the present disclosure, a third gear in externalengagement with the first gear and a fourth gear in external engagementwith the second gear may be coaxially connected to each other.

In some forms of the present disclosure, the powertrain may furtherinclude a third shift assembly configured to fix the third rotatingelement of the planetary gear to the transmission housing or connect thethird rotating element of the planetary gear to the second shaft bylinear displacement following an axial direction of the first shaft.

The present disclosure can satisfy maximum gradeability and maximumspeed required for a vehicle while reducing the capacity of a motor byproviding a plurality of shift ratios, improve electrical efficiency ofthe vehicle by realizing high power transfer efficiency using arelatively simple configuration and a relatively small weight, andprevent torque interruption and shift shock.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a first form of a powertrain for anelectric vehicle according to the present disclosure;

FIG. 2 is a diagram illustrating a second form of the powertrain for theelectric vehicle according to the present disclosure;

FIG. 3 is a table illustrating operating modes of first to third formsof the powertrain for the electric vehicle according to one form of thepresent disclosure;

FIG. 4 is a diagram illustrating a third form of the powertrain for theelectric vehicle according to one form of the present disclosure;

FIG. 5 is a diagram illustrating a fourth form of the powertrain for theelectric vehicle according to one form of the present disclosure;

FIG. 6 is a diagram illustrating a fifth form of the powertrain for theelectric vehicle according to one form of the present disclosure;

FIG. 7 is a table illustrating operating modes of the fourth and fifthforms of the powertrain for the electric vehicle according to one formof the present disclosure;

FIG. 8 is a diagram illustrating a sixth form of the powertrain for theelectric vehicle according to one form of the present disclosure; and

FIG. 9 is a diagram illustrating a seventh form of the powertrain forthe electric vehicle according to one form of the present disclosure.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

Referring to FIGS. 1 and 2 , first to third forms of a powertrain for anelectric vehicle according to one form of the present disclosurecommonly include: a planetary gear PG having three rotating elements(i.e., first, second and third rotating elements), where the firstrotating element is connected to a first shaft A1 and the secondrotating element is connected to a second shaft A2; a first motor MG1installed to selectively supply power to the first shaft A1 at two ormore gear ratios; and a second motor MG2 installed to selectively supplypower to the first shaft A1 and the second shaft A2.

The third rotating element of the planetary gear PG may be connected toa third shaft A3, and may be selectively connected to a transmissionhousing CS.

In addition, two rotating elements randomly selected from among thethree rotating elements of the planetary gear PG may be connected toeach other, such that the entire planetary gear PG can be rotatedintegrally.

Here, when the first shaft A1 is regarded as an input shaft to whichpower may be transmitted from the first motor MG1 and the second motorMG2 and the second shaft A2 is regarded as an output shaft to whichpower may be transmitted from the second motor MG2 and from whichshifted power may be output, the present disclosure may considered to beconfigured such that power that the first motor MG1 provides to theinput shaft in an adjusted manner and power that the second motor MG2provides to the input shaft or the output shaft may be readjusted usingthe planetary gear PG before being output to the output shaft.

For reference, all of the first shaft A1, the second shaft A2, and thethird shaft A3 are concentrically disposed as rotating shafts of therotating elements of the planetary gear PG. The first rotating elementof the planetary gear PG may be referred to as being a sun gear S, thesecond rotating element of the planetary gear PG may be referred to asbeing a carrier C, and the third rotating element of the planetary gearPG may be referred to as being a ring gear R.

For reference, the second shaft A2 in the drawings is expressed as OUT,and is shown to function as an output shaft to which power is output.

Forms of the present disclosure commonly include a third shift assemblyS3 fixing the third rotating element of the planetary gear PG to thetransmission housing CS or connecting the third rotating element of theplanetary gear PG to the second shaft A2 by a linear displacement alongthe axial direction of the first shaft A1.

The third rotating element of the planetary gear PG is connected to thesecond rotating element via the second shaft A2, such that all of therotating elements of the planetary gear PG may rotate integrally.

All of the rotating elements of the planetary gear PG may be configuredto rotate integrally when the third shaft A3 is connected to the secondshaft A2 as described above and when the third shaft A3 is connected tothe first shaft A1 or the first shaft A1 and the second shaft A2 areconnected.

The third shift assembly S3 may include, for example, a friction clutchable to produce a linear displacement by sliding linearly along theaxial direction while the rotation thereof is restrained by the thirdshaft A3, so as to switch between a state in which the third rotatingelement of the planetary gear PG connected to the third shaft A3 isconnected to the transmission housing CS and a state in which the thirdrotating element is connected to the second shaft A2.

In the first form illustrated in FIG. 1 , a first shift assembly S1 isprovided between the first motor MG1 and the first shaft A1 to switchbetween a state in which power provided by the first motor MG1 istransmitted directly to the first shaft A1 and a state in which powerprovided by the first motor MG1 is shifted by a gear train before beingtransmitted to the first shaft A1.

Specifically, the first motor MG1 is disposed such that the rotatingshaft thereof is coaxial with the first shaft A1, the first shiftassembly S1 includes a gear engagement unit, a hub and a sleeve of whichare disposed on the rotating shaft of the first motor MG1, a first gearG1 including a clutch gear engageable with the sleeve of the gearengagement unit is rotatably disposed on the rotating shaft of the firstmotor MG1, and a second gear G2 including a clutch gear engageable withthe sleeve of the gear engagement unit is disposed on the first shaft A1such that the rotation of the second gear G2 is restrained.

Accordingly, the first shift assembly S1 includes the gear engagementunit substantially provided on the rotating shaft of the first motorMG1, the clutch gear of the first gear G1, the clutch gear of the secondgear G2, and the like.

In addition, a third gear G3 in external engagement with the first gearG1 and a fourth gear G4 in external engagement with the second gear G2are coaxially connected to each other.

Accordingly, when the sleeve of the first shift assembly S1 is engagedwith the clutch gear of the first gear G1, power provided by the firstmotor MG1 is transmitted to the first shaft A1 sequentially through thefirst gear G1, the third gear G3, the fourth gear G4, and the secondgear G2. When the sleeve of the first shift assembly S1 is engaged withthe clutch gear of the second gear G2, power provided by the first motorMG1 is transmitted directly to the first shaft A1. As a result, thepower provided by the first motor MG1 can be transmitted to the firstshaft A1 at different shift ratios.

In addition, the second form illustrated in FIG. 2 differs from thefirst form, in that the first shift assembly S1 is disposed between thefirst motor MG1 and the first shaft A1 such that power provided by thefirst motor MG1 can be transmitted to the first shaft A1 through onegear of two external engagement gears having different gear ratios.

Here, the first shift assembly S1 includes the gear engagement unit, thehub and the sleeve of which are disposed on the rotating shaft of thefirst motor MG1. The first gear G1 and the second gear G2 are rotatablyprovided on both sides of the hub. The third gear G3 in externalengagement with the first gear G1 and the fourth gear G4 in externalengagement with the second gear G2 are coaxially connected to eachother. A fifth gear G5 is disposed on the shaft of the third gear G3 andthe fourth gear G4 such that the rotation of the fifth gear G5 isrestrained. A sixth gear G6 in external engagement with the fifth gearG5 is disposed on the first shaft A1 such that the rotation of the sixthgear G6 is restrained.

Accordingly, when the sleeve of the first shift assembly S1 is engagedwith the clutch gear of the first gear G1, power provided by the firstmotor MG1 is transmitted to the first shaft A1 through the first gearG1, the third gear G3, the fifth gear G5, and the sixth gear G6. Whenthe sleeve of the first shift assembly S1 is engaged with the clutchgear of the second gear G2, power provided by the first motor MG1 istransmitted to the first shaft A1 via the second gear G2, the fourthgear G4, the fifth gear G5, and the sixth gear G6. As a result, thepower provided by the first motor MG1 can be transmitted to the firstshaft A1 at different shift ratios.

For reference, an additional pair of external engagement gearsconfigured in the same manner as a pair of external engagement gearsincluding the first gear G1 and the third gear G3 or a pair of externalengagement gears including the second gear G2 and the fourth gear G4, aswell as, an additional transmission connecting the further pair ofexternal engagement gears to the first motor MG1, may be provided. Powerprovided by the first motor MG1 may be transmitted at another shiftratio before being input to the first shaft A1 through the fifth gear G5and the sixth gear G6.

In addition, a seventh gear G7 is connected to the first shaft A1 suchthat the rotation of the seventh gear G7 is restrained. An eighth gearG8 is connected to the second shaft A2 such that the rotation of theeighth gear G8 is restrained. A ninth gear G9 in external engagementwith the seventh gear G7 and a tenth gear G10 in external engagementwith the eighth gear G8 are disposed coaxially with each other. Thesecond motor MG2 is disposed to be connectable to the first shaft A1 andthe second shaft A2 via the second shift assembly S2 disposed betweenthe ninth gear G9 and the tenth gear G10.

For reference, the seventh gear G7 to the tenth gear G10 and the secondshift assembly S2 are common components of both the first form and thesecond form. The second shift assembly S2 includes the gear engagementunit, the hub and the sleeve of which are disposed on the rotating shaftof the ninth gear G9 and the tenth gear G10.

Since the ninth gear G9 and the tenth gear G10 are respectively providedwith a clutch gear in engagement with the sleeve of the gear engagementunit, the second shift assembly S2 substantially includes the gearengagement unit provided on the rotating shaft of the ninth gear G9 andthe tenth gear G10, the clutch gear of the ninth gear G9, and the clutchgear of the tenth gear G10.

In addition, the second motor MG2 is coaxially disposed on the firstshaft A1. The second motor MG2 is configured such that power provided bythe second motor MG2 is transmitted to the first shaft A1 or the secondshaft A2 through an eleventh gear G11 disposed concentrically on thefirst shaft A1 and a twelfth gear G12 in external engagement with theeleventh gear G11 to be coaxial with the ninth gear G9 and the tenthgear G10.

Accordingly, when the sleeve of the second shift assembly S2 is engagedwith the clutch gear of the ninth gear G9, power provided by the secondmotor MG2 is transmitted to the first shaft A1 through the eleventh gearG11, the twelfth gear G12, the ninth gear G9, and the seventh gear G7.When the sleeve of the second shift assembly S2 is engaged with theclutch gear of the tenth gear G10, power provided by the second motorMG2 is transmitted to the second shaft A2 through the eleventh gear G11,the twelfth gear G12, the tenth gear G10, and the eighth gear G8.

FIG. 3 is a table illustrating operating modes of first to third formsof the powertrain for an electric vehicle according to the presentdisclosure, in which a total of six gear stages are provided.

For reference, in the shift assemblies, “a” indicates a configuration inwhich the sleeve of the first shift assembly S1 connects or disconnectsthe clutch gear of the first gear G1 to and from power, “b” indicates aconfiguration in which the sleeve of the first shift assembly S1connects or disconnects the clutch gear of the second gear G2 to andfrom power, “c” indicates a configuration in which the sleeve of thesecond shift assembly S2 connects or disconnects the clutch gear of theninth gear G9 to and from power, “d” indicates a configuration in whichthe sleeve of the second shift assembly S2 connects or disconnects theclutch gear of the tenth gear G10 to and from power, “e” indicates thethird shift assembly S3 being configured to connect or disconnect thethird rotating element of the planetary gear PG to or from thetransmission housing CS, and “f” indicates the third shift assembly S3being configured to connect or disconnect the third rotating element ofthe planetary gear PG to or from the second shaft A2.

With reference to the form illustrated in FIG. 1 , gear stages and gearshifting of the powertrain for an electric vehicle according to thepresent disclosure will be described. In the form illustrated in FIG. 2, gear shifting is performed substantially in the same manner.

The first gear stage is realized by fixing the third rotating element ofthe planetary gear PG to the transmission housing CS, engaging thesleeve of the first shift assembly S1 with the clutch gear of the firstgear G1, and engaging the sleeve of the second shift assembly S2 withthe clutch gear of the ninth gear G9.

Here, power provided by the first motor MG1 is transmitted to the firstshaft A1 through the first gear G1, the third gear G3, the fourth gearG4, and the second gear G2. Power provided by the second motor MG2 istransmitted to the first shaft A1 through the eleventh gear G11, thetwelfth gear G12, the ninth gear G9, and the seventh gear G7.

Accordingly, both the power provided by the first motor MG1 and thepower provided by the second motor MG2 may be transmitted to the firstshaft A1. Driving in the first gear may be realized using one motor ofthe two motors, depending on the driving condition of the vehicle.

Power transmitted to the first shaft A1 as described above is input fromthe first shaft A1 to the sun gear S, i.e. the first rotating element,and is reduced by the carrier C, i.e. the second rotating element,before being output to the second shaft A2, since a ring gear R, i.e.the third rotating element of the planetary gear PG, is fixed to thetransmission housing CS by the third shift assembly S3.

The second shaft A2 is connected to one or more driving wheels via aseparate differential device or the like, such that the vehicle can bepropelled by power transferred as above.

Gear shifting from the first gear stage to the second gear stage isperformed by disengaging the sleeve of the first shift assembly S1 fromthe clutch gear of the first gear G1 and engaging the sleeve of thefirst shift assembly S1 with the clutch gear of the second gear G2.

In this case, in a state in which the torque of the first motor MG1 isreduced while the second motor MG2 is allowed to continuously supplypower, the sleeve of the first shift assembly S1 is disengaged to be inthe neutral position and then is engaged with the clutch gear of thesecond gear G2, so that the gear shifting can be performed smoothlywithout torque interruption or shift shock.

That is, even in a state in which the sleeve of the first shift assemblyS1 is disengaged to be in the neutral position, the power provided bythe second motor MG2 is continuously supplied to the first shaft A1, sothat torque can be continuously transmitted to one or more drivingwheels to prevent torque interruption. During the disengagement andengagement of the sleeve of the first shift assembly S1, the torque ofthe first motor MG1 can be reduced or completely canceled. Consequently,the sleeve of the first shift assembly S1 can be smoothly and softlydisengaged and engaged, so that excellent shifting feel can be obtained.

In the second gear stage realized as above, the power provided by thefirst motor MG1 is transmitted to the first shaft A1 directly throughthe sleeve of the first shift assembly S1 and the second gear G2 andreduced by the planetary gear PG before being output to the second shaftA2.

Gear shifting from the second gear stage to the third gear stage isperformed by disengaging the sleeve of the second shift assembly S2 fromthe clutch gear of the ninth gear G9 and engaging the sleeve of thesecond shift assembly S2 with clutch gear of the tenth gear G10.

Likewise, in a state in which the torque of the second motor MG2 isreduced or released while the first motor MG1 is allowed to continuouslysupply power to the first shaft A1, the sleeve of the second shiftassembly S2 is disengaged from the clutch gear of the ninth gear G9 tobe in the neutral position and then is engaged with the clutch gear ofthe tenth gear G10, so that the gear shifting can be performed smoothlywithout torque interruption or shift shock.

Consequently, the sleeve of the second shift assembly S2 is smoothlyconverted from a state in which the sleeve is engaged with the clutchgear of the ninth gear G9 to a state in which the sleeve is engaged withthe clutch gear of the tenth gear G10 while the power provided by thefirst motor MG1 is being continuously supplied to the driving wheels, sothat the gear shifting to the third gear stage is completed.

In the third gear stage, power provided by the first motor MG1 is inputto the sun gear S of the planetary gear PG through the first shaft A1,and power provided by the second motor MG2 is input to the carrier C ofthe planetary gear PG through the second shaft A2.

Referring to FIG. 3 , the fourth to sixth gear stages are realized in astate in which the third shift assembly S3 has connected the thirdrotating element of the planetary gear PG to the second shaft A2. Thatis, in the first to third gear stages, the third shift assembly S3 fixesthe ring gear R, i.e. the third rotating element of the planetary gearPG, to the transmission housing CS, such that the power input to thefirst rotating element of the planetary gear PG is reduced before beingoutput to the carrier C, i.e. the second rotating element, and thesecond shaft A2. In the fourth to sixth gear stages, the third shiftassembly S3 connects the third rotating element of the planetary gear PGto the second rotating element via the second shaft A2, such that thepower input to the planetary gear PG is output without reduction orincrease in speed.

For gear shifting from the third gear stage to the fourth gear stage,canceling the torque of the first motor MG1 and controlling the firstshift assembly S1 to be in the neutral position are performed from astate in which the third shift assembly S3 has fixed the third rotatingelement of the planetary gear PG to the transmission housing CS in thethird gear stage, the third rotating element of the planetary gear PG isconnected to the second shaft A2 via the third shift assembly S3, andthen the first shift assembly S1 is controlled to be engaged with theclutch gear of the first gear G1 from the neutral position. In thismanner, power provided by the first motor MG1 is transmitted to thedriving wheels, thereby completing the gear shifting. During the gearshifting, the power provided by the second motor MG2 is continuouslyprovided to the driving wheels through the second shaft A2, therebypreventing torque interruption.

Afterwards, gear shifting from the fourth gear stage to the fifth gearstage is performed. In a state in which the first motor MG1 iscontinuously transmitting power to the driving wheels, the torque of thesecond motor MG2 is reduced, and the sleeve of the second shift assemblyS2 is disengaged from the clutch gear of the tenth gear G10 and then isengaged with the clutch gear of the ninth gear G9. In addition, gearshifting from the fifth gear stage to the sixth gear stage is performed.In a state in which the second motor MG2 is continuously supplying powerto the driving wheels, the sleeve of the first shift assembly S1 isdisengaged from the clutch gear of the first gear G1 and then is engagedwith the clutch gear of the second gear G2.

As described above, also in the gear shifting from the fourth gear stageto the fifth gear stage and the gear shifting from the fifth gear stageto the sixth gear stage, shifting can be performed in a state in whichone more of the first motor MG1 and the second motor MG2 cancontinuously transmit power to the driving wheels, thereby preventingtorque interruption and obtaining smooth shifting feel.

In addition, since the powertrain for an electric vehicle according tothe present disclosure is basically configured to transmit powerprovided by the motor to the driving wheels using a related-artautomated manual transmission (AMT), superior power transfer efficiencyis obtained. In particular, in the sixth gear stage, i.e. the highestgear stage, power provided by the first motor MG1 is transmitteddirectly to the first shaft A1, and all of the rotating elements of theplanetary gear PG are restrained by each other, such that the firstshaft A1 rotates integrally with the second shaft A2. As a result, thepowertrain according to the present disclosure can output the powerprovided by the first motor MG1 without gear shifting, thereby achievingsignificantly high power transfer efficiency and increasing ormaximizing fuel efficiency of an electric vehicle.

For reference, FIG. 4 is a modified form of the first form illustratedin FIG. 1 . In the form illustrated in FIG. 4 , the second motor MG2 andgears connected to the second motor MG2 are moved to the right of theplanetary gear PG.

In addition, an output gear OG is provided on the carrier C of theplanetary gear PG, and a ring gear RG of a differential DF is engageddirectly with the output gear OG.

In the first to third forms, the first shift assembly S1 and the secondshift assembly S2 are provided in common. In contrast, a fourth form ofFIG. 5 , a fifth form of FIG. 6 , a sixth form of FIG. 8 , and a seventhform of FIG. 9 are forms in which only one shift assembly similar to thefirst shift assembly S1 or the second shift assembly S2 is provided.

First, referring to the fourth and fifth forms, the two forms areconfigured in common to include: a planetary gear PG having threerotating elements, a first rotating element of which is connected to afirst shaft A1, a second rotating element of which is connected to asecond shaft A2, and a third rotating element of which is selectivelyconnected to a transmission housing CS; a first motor MG1 installed tosupply power to the first shaft A1 at all times; and a second motor MG2installed to selectively supply power to the first shaft A1 and thesecond shaft A2.

Any two rotating elements of the three rotating elements of theplanetary gear PG may be selectively connected to each other, such thatthe entire planetary gear PG can be rotated integrally.

The first rotating element of the planetary gear PG is a sun gear S, thesecond rotating element of the planetary gear PG is a carrier C, and thethird rotating element of the planetary gear PG is a ring gear R.

A seventh gear G7 is installed on the first shaft A1 in a restrainedstate, and an eighth gear G8 is installed on the second shaft A2 in arestrained state. A ninth gear G9 in external engagement with theseventh gear G7 and a tenth gear G10 in external engagement with theeighth gear G8 are coaxially installed. The second motor MG2 isinstalled to be connected to the first shaft A1 and the second shaft A2by the second shift assembly S2 install between the ninth gear G9 andthe tenth gear G10.

The second shift assembly S2 includes a gear engagement unit in which ahub and a sleeve are provided on the rotating shaft of the ninth gear G9and the tenth gear G10.

The second motor MG2 is coaxially installed on the first shaft A1, andpower of the second motor MG2 is configured to be transmitted to thefirst shaft A1 or the second shaft A2 by an eleventh gear G11, which iscoaxially installed on the first shaft A1, and a twelfth gear G12 thatis in external engagement with the eleventh gear G11 and is coaxiallyinstalled on the ninth gear G9 and the tenth gear G10.

These forms are configured to include a third shift assembly S3configured such that the third rotating element of the planetary gear PGis fixed to the transmission housing CS or is connected to the secondshaft A2 by linear displacement following an axial direction of thefirst shaft A1.

That is, the fourth and fifth forms are forms configured to use only thesecond shift assembly S2 of the first to third forms, are nearly similarto the first to third forms with regard to the other configuration andoperations, and can realize a total of four gear stages as illustratedin FIG. 7 .

FIGS. 8 and 9 illustrate sixth and seventh forms of the presentdisclosure respectively, and include in common: a planetary gearincluding three rotating elements, among which a first rotating elementis connected to a first shaft, a second rotating element is connected toa second shaft, and a third rotating element is connected to a thirdshaft; a first motor installed to supply power to the first shaft at alltimes; and a second motor installed to selectively supply power to thefirst and second shafts. The third shaft is fixably installed on atransmission housing, and any two shafts among the first, second, andthird shafts are configured to restrain each other.

The first rotating element of the planetary gear is a sun gear, thesecond rotating element is a carrier, and the third rotating element isa ring gear.

In the sixth form of FIG. 8 , a first shift assembly is provided betweenthe second motor and the second shaft to switch between a state in whichpower of the second motor is directly transmitted to the second shaftand a state in which the power of the second motor is shifted by a geartrain and is transmitted to the first shaft.

That is, the second motor is disposed such that a rotating shaft thereofis coaxial with the second shaft; the first shift assembly includes agear engagement unit, a hub and a sleeve of which are provided on therotating shaft of the second motor; a first gear including a clutch gearengageable with the sleeve of the gear engagement unit is rotatablyinstalled on the rotating shaft of the second motor; the clutch gearengageable with the sleeve of the gear engagement unit is installed onthe second shaft in a state in which rotation of the clutch gear isrestrained; and a second gear installed on the first shaft to receivethe power of the second motor in a state in which rotation of the secondgear is restrained.

Further, a third gear engaged externally with the first gear and afourth gear engaged externally with the second gear are coaxiallyconnected to each other.

Therefore, in a state in which the sleeve of the first shift assembly S1is moved to the left side in the drawing, the power of the second motorMG2 is transmitted to the first shaft A1 through the first gear G1, athird gear G3, a fourth gear G4, and the second gear G2 in turn. In astate in which the sleeve of the first shift assembly S1 is moved to theright side in the drawing, the power of the second motor MG2 can betransmitted to the second shaft A2 without a change.

In some forms of the present form, a third shift assembly S3 isprovided. The third shift assembly S3 is configured such that the thirdrotating element of the planetary gear PG is fixed to the transmissionhousing CS or is connected to the second shaft A2 by linear displacementfollowing an axial direction of the first shaft A1.

Meanwhile, in the seventh form of FIG. 9 , a first shift assembly isprovided between the second motor and the first shaft to switch betweena state in which power of the second motor is directly transmitted tothe first shaft and a state in which the power of the second motor isshifted by a gear train and is transmitted to the second shaft.

The second motor is disposed such that a rotating shaft thereof iscoaxial with the first shaft; the first shift assembly includes a gearengagement unit, a hub and a sleeve of which are provided on therotating shaft of the second motor; a first gear including a clutch gearengageable with the sleeve of the gear engagement unit is rotatablyinstalled on the rotating shaft of the second motor; the clutch gearengageable with the sleeve of the gear engagement unit is installed onthe first shaft in a state in which rotation of the clutch gear isrestrained; and a second gear installed on the second shaft to receivethe power of the second motor in a state in which rotation of the secondgear is restrained.

Further, a third gear engaged externally with the first gear and afourth gear engaged externally with the second gear are coaxiallyconnected to each other.

Therefore, in a state in which the sleeve of the first shift assembly S1is moved to the left side in the drawing, the power of the second motorMG2 is directly transmitted to the first shaft A1. In a state in whichthe sleeve of the first shift assembly S1 is moved to the right side inthe drawing, the power of the second motor MG2 is transmitted to thesecond shaft A2 by shifting of the first gear G1, a third gear G3, afourth gear G4, and the second gear G2.

In some forms of the present disclosure, a third shift assembly S3 isprovided on the planetary gear PG. The third shift assembly S3 isconfigured such that the third rotating element of the planetary gear PGis fixed to the transmission housing CS or is connected to the secondshaft A2 by linear displacement following an axial direction of thefirst shaft A1.

Although the exemplary forms of the present disclosure have beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the presentdisclosure.

What is claimed is:
 1. A powertrain for an electric vehicle, thepowertrain comprising: a planetary gear including a first rotatingelement, a second rotating element and a third rotating element, wherethe first rotating element is connected to a first shaft, the secondrotating element is connected to a second shaft, and the third rotatingelement is selectively connected to a transmission housing; a firstmotor configured to supply power to the first shaft at all times; and asecond motor configured to selectively supply power to the first shaftand the second shaft, wherein two rotating elements among the first,second, third rotating elements of the planetary gear are selectivelyconnected to integrally rotate the entire planetary gear, wherein: aseventh gear is connected to the first shaft in a restrained state; aneighth gear is connected to the second shaft in a restrained state; aninth gear in external engagement with the seventh gear and a tenth gearin external engagement with the eighth gear are installed coaxially witheach other; and the second motor is installed to be connectable to thefirst shaft and the second shaft via a second shift assembly installedbetween the ninth gear and the tenth gear.
 2. The powertrain of claim 1,wherein: the first rotating element of the planetary gear is a sun gear;the second rotating element of the planetary gear is a carrier; and thethird rotating element of the planetary gear is a ring gear.
 3. Thepowertrain of claim 2, further comprising: a third shift assemblyconfigured to fix the third rotating element of the planetary gear tothe transmission housing or connect the third rotating element of theplanetary gear to the second shaft by linear displacement following anaxial direction of the first shaft.
 4. The powertrain of claim 1,wherein the second shift assembly includes a gear engagement unit, a huband a sleeve of which are provided on a rotating shaft of the ninth gearand the tenth gear.
 5. The powertrain of claim 4, wherein: the secondmotor is coaxially installed on the first shaft; and power of the secondmotor is transmitted to the first shaft or the second shaft by aneleventh gear installed coaxially on the first shaft and a twelfth gearin external engagement with the eleventh gear to be coaxial with theninth gear and the tenth gear.